A classic biochemical experiment nicely illustrated the point that the ribosome recognizes tRNA and not the amino acid that it is carrying. In that following observation were made. Which of them can be correct.

A. The cysteine attached to cysteine-tRNACys can be converted to an alanine by chemical reduction to give alanine-tRNACys.

B. Alanine-tRNACys introduces alanines at codons that specify insertion of cysteine.

C. Different mechanism is used to incorporate selenocyteine on tRNA as selenocysteine is incorporated into proteins by chemical modification after translation

D. Selenocysteine is generated enzymatically from serine carried on a special tRNA that is charged by serine-tRNA synthetase

E. Above examples can conclude that the translation machinery relies on the high fidelity of the aminoacyl-tRNA synthetases to ensure the accurate decoding of each mRNA

#Question id: 4399

#Unit 3. Fundamental Processes

Transcription factors can

a. exhibit cooperative binding.  b. exist as heterodimers.

c. act to repress transcription of transcription factor genes.

d. undergo conformational changes which alter activity.

e. never interact with co-repressors.

#Question id: 34169

#Unit 7. System Physiology – Animal

#Question id: 6582

#General Aptitude

#Question id: 967

#Unit 1. Molecules and their Interaction Relevant to Biology

At the subcellular level where does the urea cycle occur?

#Question id: 2857

#Unit 2. Cellular Organization

In one experiment, another protein –protein interaction is used in place of that between CAP and polymerase. This is done by taking two proteins known to interact with each other, attaching one to a DNA-binding domain, and, with the other, replacing the carboxy-terminal domain of the polymerase a subunit (aCTD), which one is appropriate result of this experiment-

I. The modified polymerase can be inhibited if the appropriate DNA-binding site is introduced near the promoter.

II. The modified polymerase can be activated by the makeshift “activator” as long as the appropriate DNA-binding site is introduced near the promoter.

III. The activator having only to help polymerase bind to the promoter